Exterior house paint contains glycol, a poison. It lasts a long time to help plasticize the paint film so it resists cracking. It's obvious that a used board in a hab that has flaking (exterior) paint would be attractive to iguanas, and very poisonous.

However, interior paint, by law, can't use glycol. Note that most claim to have zero volitiles. But they are allowed to use alkyd and water as volitiles.

The alkyd is not poisonous, takes a week or two to completely evapoorate. So interior paint is supposedly safe for iguana cage interiors. I'd use it on the outside of habs too, since it will be indoors.

Indoor paint, even though it has "no Volatiles", does have alkyds and water. The alkyds cross-link and oxidize and are totally stable (no more outgassing from the paint film), in a week or two, and water, well evaporates just like water.